Magnetic Variation

Magnetic variation, or magnetic declination, is shown on paper and raster charts, but can also be calculated using the World Magnetic Model. C source code for any platform is available at: http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml

For Windows OS, compilations with a graphical user interface (GUI) are available at:

1. http://www.ngdc.noaa.gov/geomag/WMM/wmm_gdownload.shtml and at
2. http://sites.google.com/site/navigationalalgorithms/

A World Magnetic Data PlugIn is available for OpenCPN since 2011.04.03 (version 0.1) at:
http://www.cruisersforum.com/forums/f134/world-magnetic-model-plugin-58167.html#post658775

In the example hereunder (from GUI no. 2 above) the nautical translation of “Declinacion magnética y Variación anual” is: “Magnetic variation and annual change”.